汽车制动能量回收 中外文翻译Word文件下载.docx

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汽车制动能量回收 中外文翻译Word文件下载.docx

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汽车制动能量回收 中外文翻译Word文件下载.docx

texpectmiraclesfromtuningonthebrakes-improvement,yes-butnomiracles.Therearetworeasonsforthis.First,theracingdiscbrakesystemhasbeendevelopedtoaveryhighstateindeedsothattherejustisn'

talotleftinthelineofpracticalimprovementand,second,wejustdon'

tspendverymuchtimeunderthebrakes.Ontheaverageroadracingcircuit,somethinglessthantenpercentofthetimerequiredtocompletealapisspentbraking.Therefore,afivepercentimprovementinbrakingperformance(notbrakeefficiency)wouldnetatheoreticalimprovementinlaptimeofonehalfofonepercentoraboutonehalfsecondina90secondlap.Inactuality,theimprovementwouldbesomewhatlessbecausehumanandpracticallimitationsalwayspreventusfromrealizingthefullpotentialbenefitfromanyperformanceimprovement.

Thebigpayoffofawellsortedoutbrakingsystemcomes,notfromanyincreaseinbrakingpoweritself,butintheconfidence,consistencyandcontrolabilitythatitprovidestothedriver.Thisisparticularlytruewhenitcomestocornerentry-entryspeed,placement,precisionandrepeatabilityarealldirectlydependentuponbrakingperformanceandconsistency.

Iwouldbeastonishedtolearnofamodernroadracingcarwhichwasdeliveredwithinadequatebrakes.BadlyarrangedorbadlysetupI'

mwillingtobelieve,butinadequate-NO.Thisstatementisvalidonlysolongaswedonotchangetiresize,poweroutputand/orgrossweightalloutofproportiontotheoriginaldesign.ItisdefinitelynottrueinthoseclassesofproductionbasedtouringcarandG.T.Carracingwherethesanctioningbody,throughsheerignoranceand/orbloodymindednessprohibitschangestothebrakingsystem.

BRAKINGPOWER:

WHEREDOESITCOMEFROM?

Ittakesanastonishingamountofenergytodecelerateamovingvehicle-infactittakesthesameamountofenergytodeceleratefromonespeedtoanotherasitwouldtoacceleratebetweenthetwospeeds-exceptthatwecandeceleratefasterbecausemostoftheinertialforcesareworkingforusratherthanagainstus.Theactualenergyrequiredtodecelerateourracerisgivenbytheequation:

Energy(Ib/ft)=.0335x[(mphmax)2(mphmin)2]xgrossweight(lb).Fora1760Ibcarbrakingfrom150mphto60mphwearetalkingabout.0335x[(150)2_(60)2]x1760=I,I14,344Ib/ft.Nomatterwhatterminologyweuse,thisisahellofalotofenergyabsorbedinaveryshortperiodoftime.SomebodyonceconvertedthebrakingenergyputoutbyaGT40overthetwelvehoursofSebringandcametotheconclusionthatthesameamountofenergycouldsupplytheelectricalrequirementsofafairsizedcityforagoodlyperiodoftime.Sowheredoestheenergycomefrom-whatactuallystopsthecar?

Somecomesfromtherollingresistanceofthetires-notmuch,butsome.Anotableamount,atleastathighroadspeeds,comesfromthevehicle'

saerodynamicdrag.Alittlebitcomesfromthefrictiongeneratedbetweenthemovingpartsoftheentiremechanism.Mostofit,however,mustcomefromthevehicle'

sbrakingsystemwhichconvertsthekineticenergyofvehicleinertiaintothermalenergywhichmustthenbedissipatedintotheairstream-becausewehaveyettofigureoutapracticalmethodtocollectit,storeit,anduseitforpropulsivethrust.Wereallyaren'

tveryefficient.Thischapterisdevotedtoinvestigatingthebrakingsystemitself.Weshallconvenientlyignoretheotherfactorswhichslowthecarbecausewhatwereallywanttodowiththemisminimizethemtoincreasetheaccelerationofthevehicle.

WHATWECANEXPECTFROMTHEBRAKES

Whatexactlyarewelookingforinbrakingsystemperformance?

Firstofallweneedabrakingsystemwhichiscapableofdevelopingenoughbrakingforcetoexceedthedecelerationcapacityofthetires-atanyspeedthatthevehiclecanreach-timeaftertime,forthedurationoftherace.Allracingcars,andmanymodifiedproductioncars,havesuchasystem-providedthatitisproperlyinstalled,adjustedandmaintained.Thebrakingeffortproducedmustbedirectlyandlinearlyproportionaltothepedalpressureexertedbythedriver.Further,thedrivereffortrequiredmustbereasonable,pedalpressuresmustbeneithersogreatthatGodzillaisrequiredtostopthecarnorsolightthatitwillbeeasytolockthetires.Thepedalpositionmustbecorrectlymatchedtothegeometryofthedriver'

sfootandankle,mustremainataconstantheightandshouldbereallyfirmandhaveminimumtravel.Thesystemmustdeliveroptimumbalanceofbrakingforcebetweenthefrontandreartiressothatthedrivercanmaintainsteeringcontrolunderveryheavybrakingandyetuseallofthedecelerativecapacityofallfourtires.Lastly,thesystemmustoffercompletereliability.Ifthedriverisbrakingasdeepandashardasheshouldbe,anybrakesystemfailurewillinevitablyresultinthecarleavingthecircuit.Whathappensafterthatisuptothemanupstairs.Brakefailureinaracingcaratthelimithastobeexperiencedtobeunderstood.Thisiswhyeventhemostheroicdriversareliabletogivethebrakepedalareassuringtapbeforetheyarriveattheirbrakingmarker.

Weneedavehiclesuspensionsystemcapableofdealingwiththeloadsandforcesgeneratedbyheavybrakingwithoutwheelhop,suspensionbottoming,compliance,adversecambereffects,pullordarting.Mostofallweneedadriversensitiveandskillfulenoughtobalancethecarontheedgeofthetractioncircleunderbrakingandunderthecombinationofbrakingandcornering.Ifwedonotprovidethedriverwithallofthesystemparameterslistedabove,hecannotprovideuswiththeskillanddaringnecessarytoridetheedgeofthetractioncircle.

EVALUATIONANDDRIVERTECHNIQUE

We'

llstartoutwithwhatisprobablythemostdifficultpartofthewholebrakingscene-evaluationofwhatyouhave.Measuringthebrakingperformanceofyourparticularprojectileagainstthatofthecompetitionisnoeasierthancomparinganyotheraspectofvehicleperformance-andforthesamereasons-toomanyvariablesandtoomuchegoinvolved.Thisiswhereinstrumentationisinvaluable.Thebiggestvariableis,ofcourse,thedriver.Theverylastthingthatareallygoodracingdriverlearnstodotrulywellistousethebrakes.Mostpeopletaketoolongtogetthemonhard,leavethemhardontoolongandbraketooheavilytoodeepintothecorner.AlmostinvariablythelaptimesgeneratedbytheKingofTheLateBrakersareslow.Hisadrenalinlevelisliabletobeabnormallyhighandhehasatendencytofallofftheroad.Thereareseveralreasonsforthesecharacteristics.Whenyouleaveyourbrakingtoolateyouareveryliabletoarriveatthepointontheracetrackwhereyoureallywanttostartyourturnonlytofindthatthecarwillnotturn.Itwillnotdosobecause,inyoureffortstosaveyourlife,youhavethebindersonsohardthatallofthefronttires'

availabletractionisbeingusedindecelerationandthereisnonelefttoallowthegenerationofthesideforcenecessarytoturnthecar-or,shouldyousomehowsucceedininitiatingaturn,tokeepitinabalancedcorneringstate.Inaddition,thefronttiresareliabletobeverynearlyonfireanddangerouslyclosetothecompoundtemperaturelimit.Thirdly,ifyouarestillhardonthebrakeswhentheturnisinitiated,forwardloadtransferhasunbalancedthecar,thefrontsuspensiontravelisaboutusedup,thefronttiresaresteeplycamberedand,ifthethingturnsatall,thingsaregoingtohappenabitquickly.

Ifyoupersistinbrakingtoolate,thespectatorswill"

ooh"

and"

ahh"

andbeimpressednoendandtheannouncerwillmentionyournamefrequently-notingthatyouarereallytryingoutthere.Youwillcomplainpitifullyaboutcornerentryundersteerfollowedbyanincrediblyrapidtransitiontopoweronoversteer.Theotherdriverswillpourbyyou-eitherwhileyouareexploringthegreyareasofthetrackinyourfranticscrabblefortractionoronthewayoutofthecornerwhentheyhavebothhigherexitspeedandabetterbite.Youwilldoalotofexploringasyourselfinducedundersteerforcesyouintounintentionallatecornerentries.Yourteammanagerwilleventuallycatchon,wanderoutonthecourseandobserveyourantics.Iftheensuingfrankdiscussionoftechniquedoesnotinspireyoutomendyourways,hewillseriouslyconsidereitheranotherdriver(ifyoudon'

townthecar)oranotherjob(ifyoudo).

Soanytimethatyouaregoinginnoticeablydeeperthanthecompetentopposition(assumingsimilarcars)butyourlaptimesarenotreflectingthedegreeofheroismthatyoufeeltheyshould-andthecarisenteringcornersbadly-haveagoodthinkaboutthewisdomofyourbrakingpoints.Slowinandfastoutwillbeatfastinandslowouteverytime.Ofcoursefastinandfastoutbeatseitheroftheabove-andthat'

swhatwearetryingtoachieve-butyouwon'

tcomeoutfastifyougoinwiththecarunbalancedandthefronttiresonfire.Thisisnottosaythatasuperlatebrakeapplicationfollowedbyadeliberateearlycornerentryandabitofslitheringaroundwhichusesupaportionofthetrackthatmightotherwisebeusefultosomeoneelseisnotavaliddesperationmaneuver.Itis,anditwillcontinuetobe-butitisn'

tveryoftenfastanditisevenlessoftenrepeatedlyfast.

THEBRAKEPEDAL

Havingdisposedofthesystemactuator,itistimetodiscusshardware.Wewillbeginwiththebrakepedalsinceitistheclosestparttothedriver.Thebrakepedalshouldbeverystrong-andsoshoulditsattachmenttothechassis.Thismaysoundverybasicandabitridiculous-andsoitshould.Anyfoolshouldbeabletofigureoutthatifthebrakepedal,oranyoftheassociatedbits,fractures,

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